The invention relates to an injection laser in which the laser beam can be moved in a plane substantially parallel to the injecting p-n junction which is formed in a semiconductor body between two semiconductor regions of mutually opposite conductivity types and which adjoins an active zone in the semiconductor body, the semiconductor body comprising two oppositely located side surfaces between which an optical resonator is determined and two oppositely located major surfaces substantially parallel to the p-n junction which are provided with contact regions for passing a current across the p-n junction, a first of said contact regions being divided into two sub-contact regions with which the current distribution across the p-n junction can be controlled.
The said side surfaces may be at least partially-reflecting surfaces and may in that case themselves form the optical resonator. However, the optical resonator may also be determined by lattice structures in the semiconductor body as in the case, for example, in distributed feedback lasers. In this case the said side surfaces need not be reflective. In lasers of the conventional type the said side surfaces are substantially perpendicular to the plane of the p-n junction. However, other configurations are also possible in which, for example, said surfaces are bevelled by means of etching so as to obtain total reflection.
The active zone is to be understood to mean the region near the p-n junction in which during operation he amplification is so large that the spontaneous emission in said region changes into laser action when the current density through the p-n junction has reached a certain threshold value.
A contact region is to be understood to mean herein a conductive layer of, for example, a metal provided on the semiconductor body or a comparatively low-ohmic semiconductor region which is formed in the semiconductor body and which is bounded within the semiconductor body by comparatively high ohmic material and is provided with a contact or connection wire.
Injection lasers in which the laser beam can be moved are disclosed inter alia in U.S. Pat. No. 3,402,366. Said Specification describes structures in which the two sub-contact regions of the divided contact region, viewed in the direction of the laser beam, are situated on an elongation of one another and are separated from each other by a gap which is at least mainly transverse to the laser beam. The sub-contact regions have such a configuration that when the length, measured in the direction of the laser beam, of one sub-contact region decreases in the direction transverse to the laser beam, the length of the other sub-contact region increases.
Experiments have demonstrated that freedom in designing the sub-contact regions is restricted for those cases in which accurate continuous movement of the laser beam is desired. It has been found, however, that satisfactory results can be obtained only when the gap width in a direction transverse to the laser beam is sufficiently non-linear.
Because the gap between the sub-contact regions which is situated above the optical path of the laser beam locally reduces the amplification in the active zone it is also of importance for good operation of the laser that the width of the gap should be kept as small as possible.
These requirements, which are imposed upon the shape of the sub-contact regions, make the practical manufacture of the laser rather complicated.
If it is desired to operate the laser in the c.w. (continuous wave) mode, it is usually necessary to mount the laser with one of its major surfaces on a heat sink of some metal or other, for example, Cu, which is a good heat conductor. Because for this purpose the major surface used is preferably the one which is situated nearest to the p-n junction and in many cases this is the same major surface which comprises the divided contact region, the provision of the heat sink which may at most make an electrical contact with only one of the two sub-contacts is very complicated in this known laser.